Evaluation of the pregnancy prolongation index (PPI) as a measure of success of obstetric interventions in the prevention of preterm birth and associated morbidities.

ABSTRACT

OBJECTIVE: This study was undertaken to evaluate the validity of the pregnancy prolongation index (PPI) as a measure of preterm labor treatment success. STUDY DESIGN: Analysis of prospectively collected maternal and neonatal data from a national clinical database (Matria Healthcare). Included were patients with singleton, twin, and triplet pregnancies who had outpatient surveillance initiated between 18 and 34 weeks and delivered at 24 to 36 6/7 weeks' gestation with NICU admission. Each patient's PPI score was calculated via the following equation [(gestational age at delivery - gestational age at start of treatment) / (37.0 - gestational age at start of treatment)] x 100%. The impact of increasing PPI score was measured against NICU length of stay as a surrogate gauge of neonatal morbidity. Data were further stratified by gestational type and reason for delivery. RESULTS: Pregnancy outcomes of 12,642 patients (6,642 singletons, 4,326 twins, and 1,674 triplets) were analyzed. The PPI score increased in a direct, inverse linear relationship with decreasing number of NICU days. CONCLUSION: The PPI is a sensitive measure for the evaluation of treatment success in the inhibition of preterm labor and delivery.